PDCD1 and neoplasm: By constructing an ac4Cscore model and classifying liver cancer patients into ac4C-high and ac4C-low groups with different prognosis to investigate the potential intrinsic and extrinsic characteristics of tumor, Liu et al. demonstrated that patients subject to the ac4C-high group was related to more aggressive tumor phenotypes, whereas patients attributed to ac4C-low group correlated with less aggressive tumor phenotypes, indicating that ac4Cscore may be a novel biomarker that predicts patient prognosis with anti-PD1 immunotherapy and/or mTOR inhibitor treatment [276].